1. Field of the Technology
The present disclosure relates to digital printing systems, and in particular, to xerographic printers and to the simplification of the xerographic process. Key steps in the standard Xerographic printer process are the transfer and fusing/fixing of an image from a photoconductor to a substrate such as paper. The fusing of toner on paper uses more than half of the energy to operate the machine. Electrostatic transfer, itself, involves high voltages and ozone generation.
2. Description of the Prior Art
Non-thermal (cold pressure fusing) has been known as early as the late 70's and early 80's. For example, U.S. Pat. No. 4,339,194 discloses a cold pressure fusing apparatus in a xerographic device for fusing toner images on a support surface, such as a sheet of paper, by applying a plurality of pressure fusing roller strokes to a toned copy sheet.
U.S. Pat. No. 3,988,061 discloses that toner powders deposited in an image pattern on a substrate can be fixed in place by applying pressure rather than heat. This is accomplished by applying pressure in a degree normally insufficient to secure adequate fixing, but by repeating the treatment one or more times, adequate fixing is achieved. Also U.S. Pat. No. 3,854,975 discloses fixing techniques that employ the pressure developed by two hard surfaced rolls to fix toner particles on a substrate. Another proposed process passes the substrate between hard surfaced rolls in combination with the application of heat. U.S. Pat. No. 4,444,486 discloses fixing of particulate thermoplastic material arranged in image configuration by passing the substrate carrying the images between a pair of unheated pressure engaged roll members forming part of a three roll pressure fuser.
In a typical cold pressure fusing device, the substrate to receive an image is fed between two steel rolls under considerable pressure, about 1000 psi to about 10,000 psi depending on the toner design and the paper substrate. Under pressure, the toner particles yield, coalesce and are pressed into the paper. Advantages over thermal fusing include no standby power, true instant-on, durable steel rolls to last the life of the printer, improved reliability, reduced fuser service costs, fast first copy out time, process speed insensitivity, reusable fuser hardware, reduced noise (no blowers), and reduced noise and emissions.
However, prior art cold pressure fusing devices often still require an electrostatic transfer operation to move a latent image from the photoconductor to the substrate. The electrostatic transfer operation, itself, leads to its own image quality issues such as retransfer, mottle induction, Maru-hanko, fish scales, and extreme dependence on RH, substrate core condition (RH, variation in internal properties, etc) and substrate thickness. Also, electrostatic transfer does not work with conductive substrates and conductive films often used in other applications.
It is desirable, therefore, to decrease the number of subsystems and parts in the xerographic engine, as well as decrease energy use and ozone generation. It is also desirable to reduce these subsystems, not only in office and production monochrome copiers and printers, but also in very complex and quality sensitivity color printer applications.
In accordance with the present disclosure, the above advantages are extended to a wide variation of printing systems including color systems to eliminate electrostatics in the transfer system to reduce power, number of parts, and the random image defects created by electrostatic discharges.